Design and experiment of an Integrate 3-DoF adjustable QZS vibration isolation system with High-Order stability

This paper proposes a novel integrated vibration isolation system with adjustable quasi-zero stiffness (QZS) along three axes (translational stiffness in the vertical Z axis and torsional stiffness about the horizontal X and Y axes). The three degrees of freedom(3-DoF) QZS characteristic makes the isolator attenuate both even and uneven vertical external disturbance, when compared with uniaxial isolators. Unlike previous studies, this paper focuses on the analysis of the effect of high order stability and the implementation of an adjustment mechanism to handle a wide range of loads and imperfect stiffness matching. The design concept of the isolation system is first proposed, and the static modeling is conducted for each single direction. Furthermore, 3-DoF coupled third-order nonlinear governing equations of the overall isolation system are established by the Galerkin method. The key design parameters necessary for achieving 3-DoF QZS and effects of nonlinearity on the stability and equivalent cross-coupling forces are discussed in detail. Finite element analysis including post buckling and pre-stress modal analysis verifies theoretical results. Experiments on a prototype system are presented to validate the 3-DoF QZS characteristics and transmissibility curves under three axis loads.